AIPMT 2010 Physics and Chemistry Paper

Here,
Incident wavelength, λ=200‌nm
Work function, φ0=5.01‌eV
According to Einstein's photoelectric equation
eVs=hv−φ0
eVs=‌

hc

λ

−φ0
where Vs is the stopping potential
eVs=‌

(1240‌eV‌nm)

(200‌nm)

−5.01‌eV
=6.2‌eV−5.01‌eV=1.2‌eV
Stopping potential, Vs=1.2V
The potential difference that must be applied to stop photoelectrons =−Vs=−1.2V